(1) Field of the Invention
The present invention generally relates to a control apparatus for controlling a memory unit mounted in an electric equipment, and more particularly to a control apparatus for controlling a memory unit having an electrically erasable nonvolatile memory for storing information used for a process in an electrical equipment and a flash memory for storing a processing program used to execute the process in the electrical equipment.
A flash memory is a cheap memory enabling to electrically erase information therefrom, to write information therein and to read out information therefrom, and has a large capacity. Information such as programs in the flash memory can be easily rewritten under a condition in which the flash memory is actually mounted in the electrical equipment. To rewrite the information in the flash memory actually mounted in the electrical equipment, a loading program for updating the information is required. In addition, an electrically erasable nonvolatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) can store information for a long time and this information can be rewritten. Thus, it has been used in the electrical equipment as an important memory to store various items of information.
(2) Description of the Related Art
Conventionally, a vehicle portable telephone in which a memory unit including an EEPROM and a flash memory is mounted has been proposed. The essential structure of the vehicle portable telephone is shown in FIG. 1. Referring to FIG. 1, a telephone set 100 connected to a vehicle onboard adapter 200 has a Central Processing Unit 10, a power source 11, a memory unit 12 and a radio unit 13. The CPU 10 carries out a communication process in accordance with a processing program stored in the memory unit 12, so that a communication between the radio unit 13 and a remote terminal unit is carried out. The memory unit 12 has a flash memory storing the processing program and the EEPROM storing telephone numbers each of which identifies a remote terminal unit. In order to rewrite the processing program stored in the flash memory under a condition where the flash memory is actually mounted in the memory unit 12, the rewriting being performed in order to upgrade the portable telephone set 100, a memory for storing a loading program is needed. Conventionally, the memory unit 12 is further provided with a ROM (Read Only Memory) to store the loading program therein.
In addition, to rewrite the information stored in the flash memory, a program voltage (e.g. 12 v) greater than a voltage required for a normal readout operation (e.g. 5 v) must be supplied to the flash memory. Conventionally in order to miniaturize the portable telephone set, input terminals through which the program voltage is supplied are provided in the portable telephone set, and an external power supply outputting the program voltage is connected to the input terminal when the information in the flash memory is rewritten.
If a dedicate ROM storing the loading program used to rewrite the information in the flash memory is provided in the memory unit 12 as has been described above, the memory unit 12 becomes large, so that the miniaturization of the portable telephone set is prevented.
In addition, as in the conventional apparatus, described above, input terminals must be provided through which the program voltage is supplied on the portable telephone set, a connector connecting the portable telephone set to an external equipment (the vehicle adapter) becomes large.